In recent years, the demand for flatpanel display devices such as a liquid crystal display device has rapidly grown because of the thinness, lightness, and energy-efficiency of such devices. Amongst others, an active-matrix display device is adopted in various devices including mobile information devices. The active-matrix display device includes a pixel switch which switches a pixel state between on-state and off-state electrically and holds an image signal on the on-state pixel in each pixel.
As such a flatpanel active-matrix display device, an organic electroluminescent (EL) display device using self-luminescent elements is now under keen research and development. The organic EL display device does not require a backlight, and is suitable for both movie playing use because of its rapid response and cold environmental use because of its luminosity which does not decrease even at a low temperature.
In general, the organic EL display device includes a plurality of pixels arranged in a plurality of rows and a plurality of columns. Each pixel is composed of an organic EL element which is a self-luminescent element and a pixel circuit which supplies a driving current to the organic EL element, and performs a display operation by controlling the luminance of the organic EL element.
As a driving method of a pixel circuit, a voltage signal driving method is well-known. Furthermore, there is proposed a high definition display device in which the number of lines and component elements of pixels are reduced to make a layout area of each pixel minute by adopting a structure which can switch a voltage power between low and high and output both an image signal and an initialization signal from an image signal line.